Furnace



Jan. 18, 1938. R. M. PARSON$ 2,105,819

FURNACE Original Filed June 16, 1934 4 Sheets-Shet l INVENTOR ORNEY Jan. 18, 1938. R. M. PARSONS FURNACE Original Filed Jun 4 Sheets-Sheet 2 ORNEY Patented Jan. 18, 1938 UNITED STATES PATENT OFFICE FURNACE Application June 16, 1934, Serial No. 730,874 Renewed May 25, 1937 8 Claims.

This invention relates to furnaces and more particularly to pipe stills for treating hydrocarbon oils.

In heating hydrocarbon oils to high temperatures such as temperatures required for fractional distillation or for cracking, it is necessary to use precautions to prevent carbonization or coking of the oil, which tends to occur if the rate of heat transfer to the oil in the various parts of the furnace exceeds certain values, varying with the temperature and nature of the oil. At the same time it is desirable to provide for the maximum permissible rate of heat transfer so as to conserve fuel, to utilize efficiently the available heat, and to reduce the size of the furnace for a given output of oil.

It is accordingly an object of the present invention to provide a furnace having characteristics suited for the above purpose.

Another object is to provide a relatively cheap, simple, efficient and dependable furnace for the heat treatment of hydrocarbon oils.

A further object is to improve the details of construction and method of operation of a furnace of the above type.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

In accordance with the present invention the furnace is constructed to provide for the direct flow of the furnace gases from the burners to the stack connection without substantial change in direction. In a preferred embodiment the flow is upward throughout the furnace, and the stack is located directly thereover. This construction reduces the resistance to the gas flow and permits the use of a relatively low and inexpensive stack.

Another feature of the invention is the provision of side wall tubes closely adjacent the path of the flame, in a position to receive heat both by radiation and convection so as to reduce the temperature of the flame to a value such that the flame may impinge directly upon certain oil tubes without causing local overheating of the oil therein. The side wall tubes also largely shield the furnace walls from the intense radiant heat of the flame and prevent the walls from being damaged thereby.

A bank of tubes, referred to herein as convection tubes, is located in the upper part of the furnace chamber, directly in the path of the furnace gases and is so disposed with respect to the burners that the lower rows of such tubes receive radiant heat from the flame as well as heat by convection from the furnace gases. Preferably the flame is caused to impinge directly on the lower rows of tubes. 7

Other features of the invention consist in the various details of construction and operation hereinafter more fully set forth. Although the *5 novel features which are believed to be characteristic of this invention will be more particularly pointed out in the claims appended hereto, the objects and advantages of the invention and the manner in which it may be carried out may be 10 better understood by referring to the embodiment thereof disclosed in the accompanying drawings and more specifically described herein for purposes of illustration.

In the drawings:

Fig. 1 is a vertical longitudinal section through a furnace embodying the present invention and taken along the line l--l of Fig. 4;

Fig. 2 is a vertical transverse section of the fur nace taken along the line 2-2 of Fig. 1 showing 26 the intermediate tube sheets and brackets;

Fig. 3 is a vertical transverse section of the furnace taken along the line 33 of Fig. 1 showing the end tube sheets and brackets;

Fig. 4 is a horizontal section of the furnace taken on the line 4-4 of Fig.1;

Fig. 5 is a partial end section taken on the line 55 of Fig. 4;

Fig. 6 is a partial perspective view of a tube sheet;

Fig. '7 is a broken perspective view of an intermediate bracket;

Fig. 8 is a broken perspective view of an end bracket;

Fig. 9 is a sectional view showing the insulation attached to the intermediate tube sheet;

Fig. 10 is a sectional view showing the means of attaching the insulation to the end tube sheet;

Fig. 11 is an end elevation of the furnace;

Fig. 12 is a detail of the door hinge;

Fig. 13 is a detail of the door lock; and

Figs. 14 and 15 illustrate diagrammatically different sequences of oil flow in the various tubes.

In the various figures like parts have been designated by like reference characters.

Specific terms are used herein for convenience of description but it is to be understood that they are to be interpreted as broadly as the state of the :art will permit.

Referring to the drawings, the furnace is shown 50 as comprising a pair of side walls I!) and a pair of end walls H forming a rectangular furnace chamber l2. The side and end walls may be formed of refractory or heat insulating material which may be arranged in two or more layers 55 or sections, preferably separated by an air space to provide for expansion and to reduce the heat loss. The furnace floor I3, consisting of concrete or refractory material, may rest upon an earth fill and may be provided with openings l4 located in the longitudinal median line thereof to receive burners to be described. The walls may rest upon a foundation 15 such as concrete.

An external framework of structural members such as channels may provide the support for the various furnace elements. This framework may comprise vertical members l5, spaced along a the side walls and anchored thereto as by angle irons l7. Said vertical members may be anchored to the foundation l5 as by rods 20 embedded therein and secured to angle irons 2! which may be secured to the vertical members l6 as by welding.

The vertical members l6 may be joined at their upper ends by transverse beams 22 and by longitudinal beams or angle irons 23.

The furnace also comprises a hood 30 which seats on the side and end walls and may be secured to the angle irons 23 which transfer the weight of the hood 30 to the frame-work. The hood may include a door 3| which may be hinged as at 32 to permit automatic opening in response to explosions or puffs occurring in the furnace. The hood 363 communicates with a stack 33 which may be provided with a damper 34 having an arm 35 adapted for remote operation by suitable means (not shown). The stack 33 may be relatively short and may be supported directly by the hood 3!) and guyed if desired to the corners of the furnace as by guys 36.

A row of burners 40 may be located at the lower part of the furnace chamber l2 in a position to direct the flame upwardly. Preferably said burners extend through the openings M in the floor l3. The burners 40 may comprise blocks of refractory material such as fire clay or the like having flared passages U shaped similar to a Venturi tube so as to obtain an eifioient flow of gaseous fuel and a thorough mixture of the fuel and air for combustion. The outer ends of the passages 4| may be lined with a superrefractory 42 such as high chrome non-metallic refractory, preferably mixed with basic refractory oxides adapted to withstand the high temperatures of the flame.

The burners '40 may be sufliciently long to permit partial combustion to take place therein so that the flame may have reached a high temperature opposite the lower side wall tubes, to be described.

Fuel supply pipes 43 extend to each burner 49 and terminate in jets 46 at the entrance to the passages 41. The pipes 43 may be connected to a main supply pipe 44 through valves 45 by which the action of the various burners may be individually controlled.

The air supply for the burners may be obtained directly from the outside by air ducts M6 extending beneath the floor l3 and communicating with the passages 4!. In this burner the flow of the fuel gases through the passages 4i induces a flow of air through the ducts I45, and the Venturi effect serves to effect mixing of the air and fuel. The area of the passages 4i and the position and area of the jets 45 may be such that the required air flow is induced without additional blower means. It is to be noted that all of the air for combustion is automatically drawn through the passages 4| of the burners by the suction induced by the passage of fuel therethrough and is thoroughly mixed with the fuel so as to obtain rapid and complete combustion. This construction accordingly eliminates many operating adjustments and auxiliary apparatus and improves the burner efficiency. Furthermore, the cold air passing under the floor l3 acts as a cooling means and prevents excessive heating of the floor and foundation, thereby materially reducing the maintenance cost of the furnace.

The burner blocks may be entirely constructed of super-refractory but due to the high cost thereof it is preferred to use only a lining of this material as indicated at (l2'at the points of greatest heat. Such construction materially reduces the burner cost.

An inspection or clean-out door 50 may be located in one wall of the furnace such as a side wall Ill. This door may be hinged to a frame 5| secured to the framework in any convenient manner and seated in an opening 52 formed in the furnace wall for this purpose.

The oil is heated in an upper bank 53 of convection tubes and side wall tubes 10. The upper tube bank 53 may comprise a plurality of vertically spaced rows of longitudinal tubes carried in end tube sheets 54 and intermediate tube sheets 55. The tubes of the different rows may be staggered so as to obtain the fullest effect of the heat of the combustion gases. The tube sheets 54 and 55' are each provided with upper ears 55 which are engaged by stirrups 51 supported by vertical rods 58, which in turn are hung from the transverse beams 22. The various beams 22 are located above the hood 3!] and the rods 58 extend therefrom through the hood to the stirrups supporting the tube sheets. Obviously, any number of tube sheets may be employed although the four tube sheets disclosed have been found satisfactory in a particular instance.

The end tube sheets .54 may be formed of suitable material such as cast iron and may be covered with moldable insulation 59 which may be held in position by wires 65 (Fig. 10). Said Wires 60 may be secured, as by welding, to pins or nails 6|, which are cast directly in the tube sheet. The nails 6| may be bent over and the wires 65 may be twisted and/or welded thereto in the field.

The intermediate tube sheets 55 may be made of cast iron or of a material such as steel which will permit wires (to be described) to be welded thereto. They may also be covered with insulation 59 similar to that above mentioned which may be secured thereto by wires lfil.

The wires I St may be looped and secured to the tube sheet at intervals, as by welds 62, to form a mesh or network about which the insulation may be applied.

Side flanges 63 may be formed on the tube sheets 54 and 5 5 to confine the insulation 59 and to stiffen the structure. A lower flange 84 may be positioned above the two lower rows of tubes for the same purpose and the part below said flange 64 may be covered by insulation 65 which may extend around the bottom 66 of the tube sheets to protect the lower edge thereof. The insulation on the intermediate tube sheets 55 may terminate at a point short of the upper rows of tubes where the gases have cooled to a temperature such that protection for the tube sheet is not required. The end tube sheets 54 are preferably completely insulated on both sides so as to reduce heat loss through the end doors (to be described).

A set of side wall tubes it is located adjacent each side wall ill below the upper tube bank 53. The width of the furnace chamber l2 is such that the side wall tubes. are suificiently close to the flame to receive heat both by radiation and convection. Tubes 752 are carried in end tube brackets H and intermediate tube brackets i2.

The end tube brackets H are preferably made of cast iron or steel channels covered with insulation 8| similar to that above mentioned and may be hung from the end tube sheets 54 as by bolts 13.

The intermediate tube brackets 72 may be formed of alloy steel so that insulation is not required, thereby increasing the surface area of the tubes available for heat transfer. Since common bolts would tend to burn off if unprotected by the insulation and alloy bolts are expensive, the brackets ll2 may be attached to the tube sheets 55 by lugs M formed on said bracketsand having apertures '15 (Fig. 7) adapted to pass over and be supported by ears '16 extending from opposite sides of the tube sheets .55. The ears '16 may be received in suitable recesses in the side walls it! which restrict transverse movement of the assembly. The end tube sheets may be anchored by stays TI to a suitable portion of the furnace framework.

The lower ends of the brackets H and 12 may be held against the side walls H3 by stays Bil engaging ears 8! on said brackets and extending through the side walls to the vertical members it of the framework, to which they are secured. Clearance is provided around the stays 85, particularly at the inner ends thereof, to permit movement in response to expansion and contraction of the tube sheets andbrackets.

The end walls H are provided with a door 82 opposite the ends of the upper bank of tubes and with doors 83 opposite the side wall tubes, to afford access thereto. Said doors may also be lined with insulating material and may be hinged to the framework by plates 88a. and. 81a (Fig. 12) which may be welded to the framework and to the doors respectively and receive hinge pins 88. Similar plates 89 and 90 are welded to the door and framework to receive a latch pin 9! (Fig. 13). The plates may be attached by temporarily securing the door in place, as by spot welding, then welding the plates in place and releasing the door by breaking the spot weld. This ensures an accurate fit and requires only a minimum of time. An inspection door 84 may also be provided in one end wall H which may be hinged as at to a liner 86 within an inspection aperture 81 in the end wall II.

The various tubes may be connected for oil flow in any desired sequence. A preferred sequence for certain types of cracking is illustrated in Fig. 2 in which the oil inlet is indicated by pipe 92 which. leads to a tube in the top row of the upper bank 53. The various tubes are interconnected by suitable return bends to provide oil fiow through the upper bank countercurrent to the combustion gases, thence through one set of side wall tubes countercurrent tothe flow of said gases, thence through the other set of side wall tubes concurrent with said gases, and out at pipe 93. The above sequence maintains an increasing rate of heat transfer up to the point at which the oil enters the side wall tubes, thence a somewhat reduced rate of heating throughout the rest of the circuit- Another sequence is indicated in Fig. 14 in which the oil enters the top row of tubes in the convection bank 53, passes down through the three upper rows, thence up through the three lower rows, thence down through the remaining tubes of the convection bank, thence through the side wall tubes in the manner shown in Fig. 2. This sequence of flow may be advantageous where cooler oil is required in the lower tubes of the convection. bank which are subjected to the greatest heat. The cooler oil in these tubes permits a higher rate of heat transfer without carbonization or local overheating of the oil.

A further modification is shown in Fig. 15 in which the cold oil fiows downwardly through the upper tubes of the convection bank, thence through the side wall tubes, and finally through the lower rows of tubes of the convection bank in a transverse direction. In this modification the upper tubes of the convection bank constitute a preheating section which extracts heat from the gases before they are discharged to the stack. The side Wall tubes which are heated both by radiation and convection constitute the main heating section in which the oil may, for example, be brought to cracking temperature, and the lower tubes of the convection bank, which are also heated both by radiation and convection, constitute a section in which heat may be transferred at a rate to maintain the oil at the required temperature.

It is obvious that various other modifications may be employed and that the furnace is readily adaptable for various uses by changing the connections to the various tubes.

It is to be noted that the position of the side tubes close to the flame causes the tubes to receive heat by convection as well as radiation whereby the heat is more quickly extracted from the flame. Such rapid extraction of heat serves to reduce the temperature of the flame before it impinges on the lower tubes of the upper bank and to prevent carbonization or coking in such tubes due to local overheating.

The side wall tubes partly shield the side walls it from the direct heat of the flame and reduce the quantity of heat applied to the side walls so as to prevent heating of the walls to radiance.

The upper tubes of the bank 53 are heated substantially entirely by convection whereas the lower tubes of said bank and the side wall tubes besides convection heat also receive radiant heat. The construction accordingly provides a bank of convection tubes above the radiantly heated tubes and enclosedwithin the same furnace chamber. This feature is important as it avoids any substantial change in direction of the furnace gases after passing the radiantly heated tubes. In this way the resistance to gas flow is reduced to a minimum and the required fiow of gases may be obtained without using a high, expensive stack or a blower.

The side wall tubes prevent appreciable heat loss by absorption of the side walls and roof. The end walls are of comparatively small area and the heat loss produced thereby is not great.

It is contemplated that the side walls may be made comparatively thin and of inexpensive material since they are nearly completely shielded from the flame and are not required to absorb a large amount of radiant heat and to transfer such heat by reradiation to the tubes.

The mounting of all tubes directly from the outside framework simplifles the construction problem since a minimum of weight is carried by the furnace walls. By suspending the side wall tubes directly from the upper tuba sheets, relative movement between the tubes due to expansion is avoided and the necessity for expansion couplings is eliminated.

The tube sheets and brackets are so formed as to be readily assembled in the field. The insulation may likewise be applied at the point of assembly.

Although any standard method of joining the structural members may be employed, it is preferred to use all welded construction. This may be accomplished by use of simple welding devices which are readily available at the point of assembly.

Although the invention has been illustrated as embodied in a specific device, it is to be understood that various changes and substitutions may be made therein by a person skilled in the art. The invention is accordingly to be limited only by the scope of the following claims when interpreted in View of the prior art.

What is claimed is:

1. In a furnace of the class described, a tube chamber, a bank of tubes in the upper part thereof, tube sheets supporting said tubes, a structural framework, said tube sheets being supported by said framework and having ears formed at the lower part thereof, additional tubes below said bank, brackets carrying said additional tubes, said brackets being hung on said ears and supported thereby whereby the entire set of tubes may expand and contract as a unit.

2. In a furnace of the class described, a side wall, a set of side wall tubes, tube supports carrying said tubes, means suspending said supports, and a link extending through said side wall to hold the lower part of said supports thereagainst, said side walls having sufiicient clearance around said link to permit vertical movement of said supports due to expansion thereof.

3. In combination, a furnace wall, a tube sheet rigidly supported with respect thereto, said tube sheet having a transverse lug entering a recess in said wall, a tube carrying bracket adapted to hang over and be supported by said lug, and means securing the lower end of said bracket against said wall while permitting vertical movement of said bracket in response to expansion and contraction thereof.

4. In combination, a furnace wall, a tube sheet rigidly supported with respect thereto, said tube sheet having a transverse lug entering a recess in said wall, a tube carrying bracket adapted to hang over and be supported by said lug, and means securing the lower end of said bracket against said wall while permitting vertical movement of said bracket in response to expansion and contraction thereof, said means comprising rods extending through enlarged openings in said wall and anchored externally thereof.

5. An upshot oil still comprising, in combination, a rectangular combustion chamber, a convection chamber above said combustion chamber and formed as a continuation thereof, a bank of horizontal, longitudinally extending convection tubes carrying hydrocarbon oil substantially filling said convection chamber, transverse tube sheets carrying said convection tubes, a row of horizontal side wall tubes on both side walls below said convection tubes, brackets suspended from said tube sheets carrying said side wall tubes, a row of burners at the bottom of said combustion chamber spaced along the center line thereof to direct a flame between said rows of side wall tubes onto the lower tubes of said convection bank, and means to withdraw combustion gases from the top of said combustion chamber in substantially a direct line with said burners, whereby combustion gases pass through said furnace upwardly without substantial change in direction, said side wall tubes being spaced to shield the side walls from the radiant heat of the flame and being disposed adjacent the path of the flame to receive heat both by radiation and convection for rapidly extracting heat therefrom before the flame impinges on the lower tubes of the convection bank.

6. An upshot oil still comprising, in combination, a rectangular combustion chamber, a convection chamber above said combustion chamber and formed as a continuation thereof, a bank of horizontal, longitudinally extending convection tubes carrying hydrocarbon oil substantially filling said convection chamber, transverse tube sheets carrying said convection tubes, a row of horizontal radiant heat tubes extending vertically below said convection tubes, brackets suspended from said tube sheets carrying said radiant heat tubes, a row of burners at the bottom of said combustion chamber and spaced longitudinally thereof to direct the flame past said radiant heat tubes toward the lower tubes of said convection bank, and means to withdraw combustion gases from the top of said combustion chamber in substantially a direct line with said burners whereby the combustion gases pass through said furnace upwardly without substantial change in direction, said radiant heat tubes being disposed adjacent the path of the flame to receive heat both by radiation and convection for rapidly extracting heat therefrom before the flame impinges upon the lower tubes of the convection bank.

'7. An upshot oil cracking still comprising, in combination, a rectangular, elongated combustion chamber, a convection chamber above said combustion chamber and formed as a continuation thereof, a bank of horizontal, longitudinally extending convection tubes carrying hydrocarbon oil substantially filling said convection chamber, transverse tube sheets carrying said convection tubes, a row of horizontal side wall radiant heat tubes on both longitudinal side walls below said convection tubes, a plurality of vertical brackets supported only at one end, each bracket extending in supporting engagement with an entire row of said radiant heat tubes, a row of burners at the bottom of said combustion chamber spaced along the center line thereof to direct a flame upwardly between said rows of side wall tubes onto the lower tubes of said convection bank, and means towithdraw combustion gases from the top of said combustion chamber in substantially a direct line with said burners, whereby combustion gases pass through said furnace upwardly without substantial change in direction, said side wall tubes being spaced to shield the side walls from the radiant heat of the flame and being disposed adjacent the path of the flame to receive heat both by radiation and convection for rapidly extracting heat therefrom before the flame impinges on the lower tubes of the convection bank.

8. An upshot oil cracking still comprising, in combination, a rectangular, elongated combustion chamber, a convection chamber above said combustion chamber and formed as a continuation thereof, a bank of horizontal, longitudinal- 10 heat tubes, a row of burners at the bottom of said combustion chamber and spaced longitudinally thereof to direct the flame upwardly past said radiant heat tubes onto the lower tubes of said convection bank, and means to withdraw combustion gases from the top of said combustion chamber in substantially a direct line with said burners whereby the combustion gases pass through said furnace upwardly Without substantial change in direction, said radiant heat tubes being disposed adjacent the path of the flame to receive heat both by radiation and convection for rapidly extracting heat therefrom before the flame impinges upon the lower tubes of the con- 10 vection bank.

RALPH M. PARSONS. 

